The inside surfaces of ring-shape rod seals or packings dynamically seal against the outside surfaces of piston rods which are slidably mounted in the throat in the rod ends of cylinders. Thus the inside diameter (ID) of the rod seal is nominally the same as the outside diameter (OD) of the rod. Such a ring-shape packing or seal is generally installed in a fixed groove in the cylinder rod end throat. Therefore, the ring-shape rod seal or packing must be deformed to go into a throat opening approximately the inside diameter of the resilient seal to get it into the fixed groove. This invention has relation to a tool designed to easily form the seal to an assembly position where it will fit freely within a throat opening of that diameter.
Before the present invention, three main methods were used for installing such rod seals:
1. The seals were deformed by hand and picked up with needle nose pliers and installed in the groove.
2. Where the cylinder throat through which a rod seal was to be installed was no less than 2-1/2 times the cross sectional dimension of the seal, a groove alignment plug was put into the cylinder throat from the one end to terminate in alignment with the near side of the cylinder rod seal groove, the rod seal was inserted from the other end to position at least a portion of the seal in a portion of the rod seal groove, and a tool was pushed down against the seal to try to force it down into alignment in the groove.
3. A plug having the same OD as the cylinder throat was provided with three parallel pins slidably situated therein to be movable longitudinally through the face of such plug. The rod seal to be installed was positioned against the plug face and two of those pins as they extend through the face of the plug, and the operator then attempts to deform the ringshape rod seal into a generally C-shape configuration to bring an exterior portion of the ring into alignment with the opening for the third pin. With the parts cramped in this position, the third pin is pushed forward from the face of the plug to hold the rod seal in its deformed condition. The rod seal, pins and plug are then inserted into the cylinder bore until the operator believes that the rod seal is in approximate alignment with the cylinder rod seal groove, and one of the pins is withdrawn to allow the rod seal to start to snap back into shape. The plug, and hopefully the rod seal now looped over only two pins, is moved back and forth to achieve alignment of the rod seal with the rod seal groove, the remaining pins pulled back through the face of the plug to allow the rod seal to expand into its nominal ring-shape, and the plug removed.
The obvious disadvantage of methods numbered 2 and 3 is that a different plug is required for every different diameter of cylinder throat. Also, the third method requires the use of three hands or some other part of the anatomy to move the third pin into position while the ring seal is being held in its deformed condition.
Use of the tool of the invention can reduce what can take up to ten minutes by manual methods described to no more than thirty seconds.
Furthermore, many U-cup rod seals include an internal expander, this being a further ring-shape member situated inside of the U-cup shape of the outer member. When employing hand assembly, described above, this expander ring often pops loose and must be carefully and laboriously reinstalled before attempting to again force the rod seal into the cylinder rod seal groove.